Coloration in life. The coloration of the specimens examined ( Fig. 1B
View Figure
) agrees well with what was reported by Osawa & Ng (2016).

Distribution. Known from wide area of the western Pacific: Singapore, Indonesia, New Caledonia, Vanuatu, and Japan ( Osawa & Ng 2016). The previous record of P. heok from the Japanese waters was based on a specimen from Okinawa Island, Ryukyu Islands. The present specimens extend the distribution range of the species to the north, Kagoshima in Kyushu, Japan.

Habitat. Occurring on sand and mud; depths of 7–65 m ( Osawa & Ng 2016). The type specimens of P. heok are a heterosexual pair from Singapore and were collected from the tubes of Chaetopterus aff. pacificus Nishi, 2001, living on sandstones in subtidal reefs ( Osawa & Ng 2016). The specimens examined from Iriomote Island and Kagoshima were obtained from parchment tubes of Chaetopterus pacificus which usually adhere to the underside of rocks partially buried in sand or gravel bottom. These suggest that P. heok probably prefers to live symbiotically with species of Chaetopterus that have their tubes underneath rocks.

Remarks. The present specimens agree well with the original description of P. heok by Osawa & Ng (2016) in all diagnostic aspects. Two heterosexual pairs from Kagoshima (males, cl 9.0, 9.4 mm; ovigerous females, cl 10.5, 10.7 mm; RUMF-ZC-4501, 4502) are the largest known specimens.